1. Field of the Invention
The present invention relates to a lens sheet used for a display device capable of displaying different images to a plurality of viewpoints, a display panel, and an electronic apparatus.
2. Description of the Related Art
Recently, developments for displaying different images to a plurality of viewpoints in a liquid crystal display device have been conducted actively. For example, disclosed are a display device which simultaneously provides different images to a plurality of observers located in different directions as depicted in Japanese Unexamined Patent Publication Hei 06-332354 (Paragraphs 0070-0073, FIG. 10: Patent Document 1), a stereoscopic image display device as depicted in Japanese Unexamined Patent Publication 2005-208567 (Paragraphs 0009-0012, FIG. 41: Patent Document 2), etc.
All of those display devices depicted in Patent Documents are characterized to use a lenticular lens formed with cylindrical lenses to display a plurality of images to arbitrary different directions in a distributed manner.
FIGS. 15A and 15B shows a related technique, in which FIG. 15A shows a sectional view of a display panel having a plurality of viewpoints using a lenticular lens sheet (simply referred to as “lens sheet” hereinafter), and FIG. 15B is a fragmentary enlarged sectional view of the lens sheet shown in FIG. 15A. Hereinafter, explanations will be provided by referring to the drawings.
As shown in FIG. 15A, a display panel 300 includes a lens sheet 310 and an LCD (Liquid Crystal Display) panel 320. In the LCD panel 320, a thin film transistor (referred to as “TFT (Thin Film Transistor)” hereinafter) substrate 301 and a color filter (referred to as “CF (Color Filter) hereinafter”) substrate 305 are laminated via a seal member 309, and a liquid crystal 308 is sealed between the TFT substrate 301 and the CF substrate 305.
The TFT substrate 301 includes, on a plane opposing to the CF substrate 305, a thin film element region 302 where a TFT pixel switch array, a signal line, a scanning line, a pixel electrode, a TFT driving circuit, and the like are formed and includes an alignment film 304 that has undergone rubbing processing. Further, a polarization plate 303 is provided on a plane that is on the opposing side of that plane.
In the meantime, the CF substrate 305 includes, on a plane opposing to the TFT substrate 301, a counter electrode and the like forming layer 306 where a counter electrode, a metal light-shielding film, and the like are formed, a CF layer 307 constituted with a color layer, a black matrix, an overcoat layer, and the like, and an alignment film 304 that has undergone the rubbing processing. Further, the CF substrate 305 includes a polarization plate 303 and the lens sheet 310 on a plane that is on the opposite side of that plane.
Further, a backlight module, a driving IC, a flexible print cable, and the like, not shown, are mounted to complete the display panel 300 constituted with a liquid crystal display device.
In general, the lens sheet 310 is manufactured by molding a resin, glass, or the like by using a die as disclosed in Japanese Unexamined Patent Publication 2004-280087 (Paragraph 0062: Patent Document 5) and Japanese Unexamined Patent Publication 2008-203430 (Paragraph 0025: Patent Document 6) or manufactured by using a nip roll as disclosed in Japanese Unexamined Patent Publication 2000-292858 (Paragraphs 0020-0022: Patent Document 7). WO95/09372 (pp. 21-25, FIG. 8: Patent Document 3) and Japanese Unexamined Patent Publication Hei 7-281181 (Paragraphs 0044-0052, FIG. 1: Patent Document 4) disclose a lens sheet that can be manufactured in a stable size at a low cost without using a die or the like.
As shown in FIG. 15B, the lens sheet 310 of the related technique includes lens-forming protruded lines 312 and cylindrical lenses 313 provided on a substrate 311. A resin, glass, or the like is used for the substrate 311, a resin is used for the protruded lines 312, and an ultraviolet curable resin, a thermosetting resin, or the like is used for the cylindrical lenses 313. The protruded lines shown in FIG. 15B are protruded linear structures. In some cases, a function of a liquid-repellent characteristic as depicted in Patent Document 3, a function of light-shielding characteristic as depicted in Patent Document 4, and the like may be given to the protruded lines 312.
However, the lens sheet manufactured by the low-cost manufacturing method of applying a resin depicted in Patent Documents 3, 4, and the like is low in the yield.
The length of the major-axis direction of each cylindrical lens of the lens sheet (referred to as “lens length” hereinafter) is equivalent to the longitudinal length of a screen size of a display device. In the meantime, the length in the minor-axis direction of the cylindrical lens (referred to as “lens width” hereinafter) is equivalent to the size of a pixel of the display device. The radius curvature of the cylindrical lens is properly set according to the optical design of the display device, and the height of the lens (referred to as “lens height” hereinafter) is determined from the radius curvature of the lens and the size of the minor-axis of the lens. Note here that the “major-axis direction” is also referred to as a “center-axis direction” or an “extending direction”, and the “minor-axis direction” is also referred to as a “radial direction”.
Liquid crystal display devices have become more broadly distributed year after year. Nowadays, 40-inch to 60-inch types are the mainstream, and liquid crystal display devices of 100 inches or larger at the maximum are also developed. As a result, each lens size is increased. That is, the lens height becomes higher as well, so that an applied amount of a resin for the lens at the time of forming the lens becomes increased.
As a result, the lens resin may not be able stay in the sidewalls of the lens-forming protruded lines and overflow onto the top faces of the protruded lines in some cases. In that case, each lens resin may be fused into the resin of the neighboring lens, which results in having bad-shaped cylindrical lens.
For preventing the fusion between the neighboring lenses, the width of the protruded lines may be increased. However, in that case, the effective lens width becomes smaller, which causes deterioration of the light-use efficiency such as reduction in the light flux that can be used. In the display device using a lens sheet with a low light-use efficiency, it becomes difficult to project image information to a set viewpoint with a set light amount, so that the visual characteristic and the image display quality are deteriorated.
The present invention is designed in view of such issues described above. It is an exemplary object of the present invention to provide a lens sheet of a high light-use efficiency, which can be manufactured at a low cost and with high yield, and a display panel using the same, which is excellent in the visual characteristics and the display quality.